The present invention relates to air ventilation and washing systems and in particular an air ventilation system for removing grease laden air produced as the result of cooking, and a washing system for cleaning any accumulation of grease within the system.
In commercial cooking establishments where large quantities of food are cooked on an open stove or on hot grills, large amounts of air contaminated with grease is produced. For reasons of health, safety and cleanliness, the heated grease laden air must be evacuated from within the room.
The early method of removing the undesirable air was merely to have a massive exhaust fan located in the ceiling or wall pull out the contaminated air from within the room. It was very soon recognized, however, that replacement air was required to be blown into the room in order to replace the air drawn out by the exhaust fan.
Such arrangements were undesirable for a number of reasons, including the most obvious reason that any chef working in the kitchen would be subjected to enormous drafts of hot and cold air. A further disadvantage of such systems was the great expense associated with the heating or cooling requirements of the kitchen. For example, any attempt to air condition the kitchen during the summertime would require a massive cooling system to maintain the temperature due to the fact that the cooled air would be almost immediately withdrawn from the room by the exhaust fan. Comparable difficulties would be encountered during the cold season when the heated air would be removed from the room to be replaced by frigid outside air.
In recognition of the aforementioned disadvantages, air ventilation systems were devised which first forced a curtain of outside air over the cooking surface of the stove and then withdrew a mixture of the outside air and the inside air. Such ventilator systems are known as "air curtain ventilator systems", such as disclosed in the patent to Sweet, et al., U.S. Pat. No. 3,457,850, issued July 29, 1969.
In such systems, as indicated by their nomenclature "air curtain ventilator", a "curtain" of air was formed by forcing the outside air through a relatively narrow, substantially horizontally oriented opening so as to create a horizontal curtain of air over the exhaust or vapor collection chamber. Such a system is partially ineffective in removing contaminated air not immediately above the cooking surface.
Providing an exhaust system for removing the grease laden air above the stove, while solving one problem, created additional problems. As indicated above, the air above a kitchen stove, especially in a commercial establishment such as a restaurant, is heavily contaminated with grease from the foods being cooked. The collection of any quantities of grease presents a highly volatile source of fire. Grease filters located in the air exhaust system may remove a large quantity of the grease. The grease filter is periodically removed and either cleaned or replaced by a new grease filter.
The grease filter, however, does not remove all of the grease from the air, some of the grease passing through the filter and condensing on the surfaces of the grease duct and on the exhaust fan. The collection of the grease in a normally inaccessible area, in association with the high temperatures generated by the cooking surface, created a fire hazard.
The grease collected within the grease duct is such that they must be thoroughly cleaned, depending upon their use, every three months. Due to the general inaccessibility of the grease ducts, the manual cleaning of the ducts is costly and highly inefficient. Large collections of grease may remain in the ducts for many weeks at a time. During such times the grease duct and other equipment are highly susceptible to fire. More frequent manual cleanings of the duct, however, is prohibitively expensive.
Recognition of the potential fire hazard presented by grease accumulations in the grease duct and the undesirability of having the ducts manually cleaned led to the development of automatic duct cleaning devices such as disclosed in the patent to Lawson, U.S. Pat. No. 3,795,181, issued Mar. 5, 1974. Such an automatic duct cleaning device forced hot water and a cleaning solution through a number of rotating spraying outlets on a hollow tube by the use of a fluid forcing device in order to spray the inside surfaces of the duct. The cleaning solution would homogenize the grease on the surfaces of the duct which would then flow down the sidewalls of the duct to be collected in a grease trap or other receptacle. Upon the completion of the washing cycle, the water and cleaning solution within the hollow tube would, under the force of gravity, collect within the housing of the means for forcing the cleaning fluid through the outlets. In periods of extreme cold, the water and cleaning solution would freeze, rendering the cleaning system inoperable.
While the automatic duct cleaning device of Lawson went a long way towards reducing the possibility of a fire occurring within the grease duct, such a possibility was not completely eliminated. Under certain circumstances grease might still collect in the duct, such as between washings, should the interval between washings be too long or should the washing equipment become inoperative and not be promptly fixed.
Chemical fire extinguisher systems conventionally located suspended from the vapor collection chamber above the cooking surface, responsive to excessive heat on the cooking surface, have been used. Ordinarily such fire extinguishing systems would not be activated by heat generated within the grease duct unless there was a substantial fire actively present within the duct. In any event, such a fire extinguishing system would serve only to extinguish the fire in the vicinity of the cooking and would have no effect on any fire within the air ventilation system.
The "air curtain" ventilators, such as identified above, have been partially or wholly unsatisfactory because they are so constructed that they cannot be installed in existing building structures or in new building structures without provision of large space between the ceiling and the room for the replacement or "make-up" air distribution baffles and hood structures. The low pressure, uniform distribution of external make-up air and mixing thereof with room air and with contaminated air just above the stove or grill have also posed contamination problems.